Depends on your incoming water - do you have ordinary hose pipe? I have 1/2" hose from an outside tap - John Guest 1/2" tube fits snugly inside garden hose, just need a couple of jubilee clips for safety. Inlet side of pump is via a reducing bush and John Guest push fit. Outlet is also reducing bush and John Guest to 1/2" tube and then to RO system.
This was how I set it up in the first place, works fine so no need to change anything.
You could have incoming water straight to first prefilter, then 1/2" tubing to pump then to membrane.
I'm not a fan of hozelocks on RO systems, too much pressure and danger of connectors 'popping off'